L3T4+ T cells able to mediate parasite-specific delayed-type hypersensitivity play a role in the pathology of experimental Chagas' disease.

During the chronic phase of infection with the parasite Trypanosoma cruzi, mice develop inflammatory lesions in the heart and skeletal muscles, as well as in peripheral nerves and the liver. We demonstrated the presence, in the blood of chronically infected mice, of L3T4+ T cells able to transfer a specific T. cruzi delayed-type hypersensitivity (DTH) reaction. Transfer of the chronic inflammatory lesions was obtained by injecting Lyt-2+-depleted lymphocytes from either lymph node or blood of infected mice. T cell lines were established from the chronically infected mice by culturing peripheral blood lymphocytes or lymph node cells with either T. cruzi extracts (TC) or mouse peripheral nerve extracts (PN). Those cell lines that presented an L3T4+ phenotype were also able to specifically transfer a local DTH reaction to naive recipients. Examination of the antigen specificities of these TDTH lines revealed three types: those that mediated a DTH reaction to TC, those that responded to both TC and PN and those that provoked a DTH response when injected with subinflammatory doses of an irrelevant antigen. Some of the lines, when injected into the sciatic nerve of naive recipients, provoked demyelination of the type observed in chronically infected animals. These results suggest that T. cruzi and the host nervous system share common epitopes that can be recognized by TDTH cells.